Electrochemical depositions of calcium phosphate film on commercial pure titanium and Ti–6Al–4V in two types of electrolyte at room temperature

Electrochemical depositions of calcium phosphate film on commercially pure titanium (cp-Ti) and Ti–6Al–4V in two types of electrolytes, mono-calcium phosphate monohydrate (MCPM) based aqueous solution and supersaturated calcium phosphate solution (SCPS), were carried out by the cathodic polarization. The calcium phosphate coating layer was successfully deposited on cp-Ti and Ti–6Al–4V under 3 mA/cm² current density for 45 min. The major phases that appeared in the film were DCPD (brushite) co-existed with octa-calcium phosphate (OCP). After soaking in revised simulated-body-fluid (r-SBF), the amorphous bone-like apatite became a single phase within a day for the specimen obtained from MCPM electrolyte. The specimens obtained from SCPS electrolyte took a week to complete the apatite precipitation in r-SBF. From the scratch test, the highest critical load of 87.2 N was obtained from the as-deposited rod-like DCPD on cp-Ti substrate. The critical load was decreasing almost 50% for all of the specimens after apatite precipitation in r-SBF. The decrease of critical load might result from loosening of the film structure during immersion of the specimens in r-SBF. The thickness of the films was 44–55 μm in average, which satisfied the qualification for using as an implant material.     

A Suitable Method for Ecovehicles to Control Surge Voltage Occurring at Motor Terminals Connected to PWM Inverters and to Control Induced EMI Noise

A method that is suitable for ecovehicles, which controls the surge voltage appearing at motor terminals that are connected to a pulsewidth modulation inverter with short leads that are less than the critical cable length (i.e., the shortest length at which full reflection may occur), is described here. Also, a method to control electromagnetic interference (EMI) noise, which is induced by the surge voltage, is discussed. Ecovehicles have the problem where insulation degradation of motors occurs due to the surge voltage being repeatedly applied to motor terminals during long lifecycles. EMI noise such as the shaft current and the radiated noise, which are induced by the generated surge voltage, easily diffuse into other electric devices due to the high-density packaging structure. The diffused EMI noise may cause a malfunction of the vehicle controller. An EMI noise controller is studied, which can meet the high-density packaging requirements for ecovehicles like electric vehicles. The EMI noise controller is attached on the motor terminals and simultaneously suppresses the surge voltage and the noise. After clarifying surge voltage characteristics and a circuit model for expressing the surge phenomenon through experiments and simulations, an EMI noise controller is proposed, which uses a multilayer printed power circuit technique. It is verified through simulations and experiments that the proposed controller has the ability to simultaneously control the surge voltage and the EMI noise, such as the radiated noise and the shaft current (the bearing current), which are induced by the surge voltage.     

Electron microscopic study of intercalated duct cells in the chicken pancreatic islet and effects of tolbutamide administration

Intercalated duct cells are present in the alpha and beta islets of chicken. The intercalated duct cells adhere to each other via intercellular junctional complexes at the apical side, projecting many microvilli and a few cilia into the lumen. They also extend slender cytoplasmic processes between the islet endocrine cells. These intercalated cells appear to have a stellate form, and to wrap their cytoplasm around endocrine cells. Administration of tolbutamide led to increased electron density in the cytoplasm of intercalated duct cells. Lysosomes are present in these cells in various numbers and sizes and tend to increase with time after administration of tolbutamide. These observations suggested that the intercalated ducts not only pass through the islet, but also play a role in supplying islet cells.     

Fracture toughness of gamma-base titanium aluminides

Effects of microstructures, alloying additions, and processing routes on the room- and elevated-temperature fracture toughnesses of gamma-base titanium aluminides were investi-gated. Microstructure was found to have a strong influence on the fracture toughness both at room and elevated temperatures. Lamellar microstructure materials exhibited high fracture toughness compared with duplex microstructure materials, which in turn possessed high fracture toughness compared with the equiaxed microstructure materials. Alloying additions affected the fracture toughness at elevated temperatures significantly. The addition of chromium improved the low-temperature fracture toughness (below 800 °), while the addition of niobium increased the fracture toughness above 800 °. Grain size refining, as a result of isothermal forging after casting and heat treatment, had less influence on the fracture toughness. Formerly Graduate Student, Nagaoka University of Technology     

Optical limitations to cell size reduction in IT-CCD image sensors

We have determined the practical limits of cell size reduction in interline-transfer charge-coupled device (IT-CCD) image sensors, which result from diffraction occurring at the aperture above the photodiode. We have found that image cell size cannot be reduced to a level for which aperture width would fall below about 0.2 μm. We have also found, however that image cells with greater than 0.2 μm aperture size are sensitive over the entire wavelength range of visible light, and that sensitivity can be increased by thinning the photoshield film     

STATIC AND CYCLIC FRETTING FATIGUE BEHAVIOUR OF SILICON NITRIDE

A cyclic fretting fatigue test machine was constructed. The piezoelectric bimorphs were used as actuators for cyclic loading and fretting motion at the resonance frequency of the system. Fretting fatigue tests under static and cyclic loading conditions were carried out using HIP-sintered silicon nitride. From the experimental results, it was found that fretting fatigue strengths under the two test conditions were identical and hence the effect of cyclic loading on fretting fatigue strength of silicon nitride was almost negligible. A fretting crack initiated in a very early stage of the fatigue life at the position of the maximum frictional stress in the contact area. Fretting fatigue life prediction based on fracture mechanics was also carried out. The predicted lives were in good agreement with the experimental results.     

A 1/4-inch 380 k pixel IT-CCD image sensor employing gate-assisted punchthrough read-out mode

A newly developed 1/4-inch 380 k pixel IT-CCD image sensor features a novel cell structure in which signal charges are read out from a photodiode (PD) to a vertical-CCD (V-CCD) in a gate-assisted punchthrough mode. The cell structure, fabricated through the use of high energy ion implantation technology, enables both deep PD formation and transfer-gate (TG)/channel-stop (CS) length reduction. Deep PD formation helps increase sensitivity per PD unit area, and TG/CS length reduction widens both PD and V-CCD areas. Although the cell size is small (4.8 /spl mu/m (H)/spl times/5.6 /spl mu/m (V)), the sensor achieves both high sensitivity (35 mV/lx) and a high saturation signal (600 mV).<>     

A method for verifying sector conditions in nonlinear discrete-timecontrol systems

The stability of a discrete feedback system with a continuous broken-line nonlinearity is considered. Many nonlinearities in practice are included in this class. Sufficient conditions for this type of nonlinear feedback system to be asymptotically stable in the large are developed using the contraction mapping theory. It is then shown that Kalman's conjecture (1957) for a feedback system with a sector nonlinearity also applies to discrete systems under a restricted sector condition. A method for obtaining this restricted sector by solving a quadratic equation is presented     

Evaluation of fretting wear based on the frictional work and cyclic saturation concepts

It is time consuming or even impossible to simulate the whole process of fretting wear, since it always involves millions of cyclic loadings. This paper focuses on the modeling and evaluation method of fretting wear for the typical bridge type fretting test with a flat pad. The frictional work on the contact interface is chosen as the parameter to evaluate the fretting wear. To verify the fretting wear model, the predicted wear profile is compared with that obtained by the experimental results. Fretting wear always includes plastic deformations due to the edge stress singularity. The effect of cumulative plastic deformation is also taken into account in the wear model. The role of the coefficient of friction at the contact interface on the fretting wear has also been discussed.